NEXAFS study of 2LiF–MgB2 composite

Synthesis of lithium borohydridofluorides may pave a new way to pursue improved hydrogen storage properties of LiBH4 as reversible hydrogen storage materials that fit the fuel cell application. The main products of the hydrogen absorption by 2LiF–MgB2 composite are MgF2 and LiBH4. In addition to them, LiBH4−xFx compounds might be present during hydrogen absorption–desorptions and play important role on their kinetics and reversibility.First results of Near Edge X-ray Absorption Fine Structure (NEXAFS) at the B K-edge (193 eV) for LiF–MgB2 composite with molar ratio (2:1) are presented. Obtained results indicate a formation of mixed borohydrides/borofluorides of the type of LiBH4−xFx, thus suggesting fluorine substituting for hydrogen.

► First results of NEXAFS at the B K-edge (193 eV) for 2LiF–MgB2 are present.
► Some changes in the local structure of B atom in [BH4]− groups were identified.
► NEXAFS spectra give hints to the existence of a mixed LiBH4−xFx phase.